They were lovers. They were accomplices. Together, they became two of Britain's most notorious murderers.

Ian Brady and Myra Hindley have become almost inseparable from the story of the Moors Murders. Yet behind the crimes was a disturbing relationship built on attraction, obsession, manipulation and violence.

What drew Myra Hindley to Ian Brady? How did their relationship develop from romance into something far darker? And how did two seemingly ordinary people become involved in crimes that would horrify a nation?

The Devil Knows looks beyond the headlines to examine the relationship between Brady and Hindley?their meeting, their growing obsession with one another, and the dark path that ultimately led them to the murders.

More than sixty years later, the Moors Murders remain one of the darkest chapters in British criminal history.

But at the centre of this story lies a disturbing question:

What was it about their relationship that allowed them to descend so far into darkness?